Polar - We've given our Polar Flow app a bit of a refresh—we've also made it possible to share your training data directly from the app to Facebook. Well worth an update:
User Manual
How to Sync the Polar Loop: 11 Steps (with Pictures) - wikiHow Health
Sync your sleeps from Polar Flow to Google Fit : r/Polarfitness
Incomplete data in Flow after syncing? | Polar Global